Chapter 4
Adiabatic Quantum Computing and Quantum Annealing

Love’s a different sort of thing, hot enough to make you flow into something, interflow, cool and anneal and be a weld stronger than what you started with.
— Theodore Sturgeon

In the previous chapter, we studied how to formulate different combinatorial optimization problems as QUBO instances that, in turn, could be rewritten as the optimization problem of finding a state with minimum energy in an Ising model system. In this chapter, we will use this fact to introduce a way of using quantum annealers — a special type of quantum computer — to try to find (approximate) solutions to those combinatorial optimization problems.

But, in order to do that, we first need to talk a little bit more about Hamiltonians and their ground states, as well as the central role they play in adiabatic quantum computing.

The topics that we will cover in this chapter are as follows:

• Adiabatic quantum computing

• Quantum annealing...